Geographic Bias as a Methodological Condition in Ageing and Built Environment Research: Equity, Feasibility, and the Limits of Indicator Portability

In ageing and built environment research, unevenness in evidence across spatial contexts constitutes a methodological condition rather than a simple coverage gap, with direct implications for how accessibility, usability and fairness are conceptualised and measured. Research on built environments for older adults has largely relied on urban evidence. Although findings from cities remain valuable, this focus influences how concepts are defined, which indicators are considered valid, and how far results can be generalised. Indicators designed for high-density urban settings often capture service availability well but have limited validity in low-density or resource-scarce environments. In such contexts, the presence of nearby services is frequently equated with accessibility, and accessibility is often assumed to imply usability. This paper synthesises review and measurement research to identify three mechanisms sustaining urban bias: urban-focused sampling, limited transferability of common indicators, and exposure definitions that assume density and reliable infrastructure. Building on this analysis, the study proposes a measurement framework that explicitly takes principles of fairness into account. This framework is organised around four analytical lenses: distribution, recognition, participation and sustainability. Matching sampling strategies, spatial classifications, measurement strategies and reporting practices to local settlement characteristics is critical to ensuring that conclusions are appropriately limited to what indicator-based evidence can validly support.